Internal combustion engines have a cylinder block and a cylinder head, which are connected to one another at the assembly faces thereof to form the at least one cylinder, i.e. combustion chamber. The cylinder block includes cylinder bores to hold the pistons. The cylinder head generally serves to accommodate the valve gear. The valve gear includes the intake and exhaust valves as well as the valve actuating mechanism required to move the valves.
Typically, the inlet ducts, which lead to the inlet ports, and the outlet ducts, i.e. the exhaust lines, which are connected to the outlet ports, are at least partially integrated into the cylinder head. The exhaust lines of the outlet ports of each individual cylinder are generally brought together—within the cylinder head—to form a component exhaust line. The exhaust lines are combined into an overall exhaust line referred to generally and in the context of the present disclosure as an exhaust manifold. Downstream of the at least one manifold, the exhaust gases are then fed to a radial turbine, e.g. the turbine of an exhaust turbocharger and, if appropriate, are passed through one or more exhaust gas after treatment systems.
The production costs for the turbine are comparatively high since the material—which frequently contains nickel—used for the thermally highly stressed turbine casing is expensive, especially in comparison with the material that is preferably used for the cylinder head; e.g. aluminum.
It would be advantageous in terms of costs if it were possible to provide a turbine which could be manufactured from a less expensive material, e.g. aluminum. To enable less expensive materials to be used to produce the turbine, turbines may be provided with a cooling system, e.g. a liquid cooling system, which greatly reduces the thermal stress imposed by the hot exhaust gases on the turbine and on the turbine casing and hence allows the use of materials less capable of bearing thermal stresses.
In general, the turbine casing is provided with a coolant jacket in order to form the cooling system. This includes both concepts in which the casing is a casting and the coolant jacket is formed as an integral part of a monolithic casing as part of the casting process, and concepts in which the casing is of modular construction, where a cavity which serves as a coolant jacket is formed during assembly.
A turbine configured in accordance with the last-mentioned concept is described by German Laid-Open Application DE 10 2008 011 257 A1, for example. A liquid cooling system for the turbine is formed by providing the actual turbine casing with a shell, thus forming a cavity, into which coolant can be passed, between the casing and the at least one shell element arranged at a distance. The casing with the shell added then includes the coolant jacket. EP 1 384 857 A2 likewise discloses a turbine, the casing of which is provided with a coolant jacket. DE 10 2007 017 973 A1 describes a kit for the formation of a vapor-cooled turbine jacket.
In principle, there is the possibility of providing the liquid cooling system of the turbine with a separate heat exchanger or the heat exchanger of another liquid cooling system. However, one factor that has to be taken into account in this context is that the amount of heat to be absorbed by the coolant in the turbine can be 40 kW or more if materials with little resistance to thermal stress, such as aluminum, are used for the production of the casing. Removing such a large amount of heat from the coolant in the heat exchanger and dissipating it to the environment by means of an air flow proves to be problematic, as surface area available for heat transfer may be limited.
In addition to the heat exchanger of the engine cooling system, modern motor vehicles often have additional heat exchangers, in particular cooling devices. For example, charge air coolers, oil coolers, EGR coolers, transmission fluid coolers, air conditioning condenser, etc., may all be arranged in or near the front end zone. Thus, owing to the very restricted space conditions in the front end zone and the large number of heat exchangers, it may not be possible to dimension the individual heat exchangers as required. Also, there may be no possibility of arranging a sufficiently large heat exchanger for liquid cooling of the turbine in the front end zone to allow dissipation of the large amounts of heat. There has therefore to be a compromise between cooling capacity and material in the design configuration of a cooled turbine.
The inventors herein have recognized the above issues and have developed a system to at least partly address them. Accordingly, an internal combustion engine is provided. The engine comprises a turbocharger including a turbine having a coolant jacket integrated in a housing of the turbine, and an oil circuit, the oil circuit coupled to the coolant jacket of the turbine.
The present disclosure may provide several advantages. For example, it makes it possible to dispense with materials with the capacity to bear high thermal stresses, especially those containing nickel, for the production of the turbine casing, since the present description also makes provision for the turbine to be provided with a cooling system. The cooling system ensures a reduction in temperature and hence reduces the thermal stress on the material, rendering materials resistant to high temperatures unnecessary. On the other hand, utilizing oil as a coolant results in a cooling capacity that is not so large that materials with only little resistance to thermal stress, such as aluminum, can be employed. This approach makes the use of expensive materials unnecessary without dissipating excessively large amounts of heat in the context of turbine cooling.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.